The present invention relates to a centrifuge arrangement and, more particularly, to a continuously-running centrifuge having a relatively thin-walled, one-piece, conically-shaped container which is relatively free of undesirable vibrations and which is further free of out-of-true rotation. The present invention further relates to a rolling method of making the conically-shaped container.
It is highly desirable to build a centrifuge arrangement so that it is, among other factors, vibration-free, lightweight, thin-walled, concentrically-running, inexpensive, and efficient in its use of energy. However, the prior art has had difficulties in providing centrifuges with these advantageous characteristics.
Thus, the prior art has proposed casting the container which receives and rotates the mixture to be separated into its constituent parts. However, casting techniques generally provide the container with an initial thickness of about 30 mm and a final machined thickness of between 12 mm and 15 mm.
The prior art has also proposed welding the containers out of separate metallic plates. These plates generally have an initial thickness of about 15 mm and a final machined thickness of between 8 and 10 mm.
In both of these aforementioned methods of making the container, there are several related problems. First of all, the container must always be subsequently machined in order to try and eliminate the unavoidable imbalances inherent in the container which will cause the container to rotate out-of-true. This machining is evidently very expensive. Secondly, because of structural rigidity reasons, the cast container must be maintained thicker than the welded container. However, on account of the subsequently required machining operation in both techniques, the containers cannot be made arbitrarily thin. Thus, both types of containers are still too relatively thick, even after the subsequent machining. The high weight of the containers requires an additional amount of energy input in order to rotate the container. Thirdly, the relatively heavy containers of the prior art have a further disadvantage in that intermittent feeding of the mixture into the container causes strong vibrations which vibrate the base of the centrifuge and tend to displace the entire housing of the arrangement.
It has further been proposed in the prior art to reduce the wall thickness of the container by a deep drawing operation. The containers made by this technique, however, have not been satisfactory, inasmuch as the male tool must repeatedly engage the female tool with different forces of engagement. Thus, the true-running characteristic of this type of container is impaired.
Finally, the prior art has also proposed various techniques for securing the container to a rotor of the centrifuge. These approaches have included welding, soldering and riveting both parts together. However, all of these techniques are disadvantageous because the tensions and strains introduced into the container itself will subsequently be released and distort the precise, true-running characteristic of the container. Even if the container is not subsequently machined, a pure screw-type connection disadvantageously influences the true-running characteristic of the container.